High volume, high yield production
Posted date : Dec 4, 2009

At the 45nm node, substrate quality and uniformity are more critical than ever before to ensuring the best possible device performance. This is especially true in SOI wafers, where the substrate’s electronic structure is engineered to play an active role in enhancing carrier mobility or decreasing leakage current.

Figure 1. SP2XP optical design. While the wafer spins, the darkfield subsystem illuminates a spot on the wafer from a normal or oblique incidence. Darkfield collectors span either narrow or wide solid angles. A separate, normal-incidence brightfield DIC channel operates simultaneously with either of the darkfield channels.

Semiconductor manufacturers producing SOI-based devices utilize the Surfscan SP2XP as part of a comprehensive yield management strategy. Featuring improvements in sensitivity, production throughput and killer defect classification, the Surfscan SP2XP is used for incoming wafer quality control, process tool monitoring and unpatterned wafer defect inspection. It is designed to help chipmakers accelerate production of their leading-edge, SOI-based devices.

High speed, high sensitivy

The Surfscan SP2XP employs several optical technologies (Figure 1) to ensure high sensitivity and broad defect type capture on both bare SOI substrates and blanket films. These include: UV illumination, normal and oblique incidence angles, narrow and wide collection channels, and selectable polarizations. An optional ultra high sensitivity mode allows the Surfscan SP2XP to be used for development of next-generation chips on most advanced SOI substrates.

The Surfscan SP2XP includes changes in opto-mechanics, electronics and software that results in up to 36% throughput increase compared to its predecessor, the Surfscan SP2. This allows IC manufacturers to inspect more wafers per hour or to use a higher sensitivity setting without a loss in throughput.

Figure 2. Comparison of SOI defect sizing from the Normal-Narrow and Oblique-Wide channels. Voids are clearly distinguishable from particles (LPDs).

Better binning, better yield

The patented multi-channel architecture and innovative algorithms enable the Surfscan SP2XP system to automatically distinguish intrinsic defects from re-workable defects. Examples of this defect binning capability include the separation of particles from voids and residues on SOI substrates (Figure 2), polish-induced defects from particles on CMP polished wafers, stains from particles on post-wet clean wafers, and yield-impacting LLPD from particles on films. Chipmakers’ use of this improved defect classification capability leads to fewer scrapped wafers and greater yield of high-performance, SOI-based devices.

Soitec, the world’s leading SOI wafer manufacturer, was a key beta partner with KLA-Tencor in development of the Surfscan SP2XP technology, and was one of the first substrate manufacturers in the world to put the system into production. By utilizing the Surfscan SP2XP for incoming wafer quality control and process tool monitoring, IC manufacturers ensure rapid development and production ramp of SOI-based devices.

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